At one point I think clicking Cancel would return state to Publish Immediately (I vaguely remember it being a topic of discussion a couple of releases ago), but that was overriding the normal ok/cancel behavior. I've never had any problem with setting the date and time back to right now manually. Is it really that hard to look up in the corner of your computer screen to see what time it is and enter it? I'm all for making the UI easier, but in cases where the use case is relatively narrow, we have to weigh adding more stuff to reduce work on the part of the user needing the new behavior with adding clutter for all the users that don't need the behavior. If we had any stats on how often a post goes from being scheduled to being published immediately that would be useful.

I'd suggest a plugin, but let's face it, such a small change to UI probably wouldn't get a lot of publicity in the world of plugins. Maybe wordpress.com (and/or any other person/business out there running a customized/hosted WP setup that could gather stats on usage) could implement a feature like this, and we could observe the usage stats for a while to help determine if it's needed for core.

In meantime, adding this tickt to UI group's list of UI issues that might need addressing.

Does this need a UI? Surely when you edit the schedule date the "cancel" link should just remove the schedule. It works like this if you edit the schedule date multiple times prior to actually scheduling the post.